I am implementing Cytoscape.js web 2.0. I am a bit confused on the difference between load and add. I understand that in load, we do not need to specific the positions of the nodes. I used add to add a node which works when I include the position attribute, but the edges do not show even when I add the position attribute. Also, what is the difference between load and add behind the scenes? I believe that load renders the entire graph, so every time we use load, it would re render the graph. It seems that add does not do that which is good for operational costs? Is that true?